Rotary blade for mulching lawn mower

ABSTRACT

Rotary blade for a power-driven lawn mower comprising an elongate body terminating at each end in a plurality of integral cutting fingers parallel to and displaced successively below and above the plane of the body with each finger defining a different plane and the upper surfaces of the leading edges of the fingers and the lower surfaces of their trailing edges chamfered to form cutting edges, whereby top-to-bottom reversal of the blade presents as leading cutting edges those that were trailing edges.

United StatesPatent Anderson [54] ROTARY BLADE FOR MULCHING LAWN MOWER[72] Inventor: Charles I. Anderson, 7399 Main Street, Downers Grove,[11. 60515 [22] Filed: Feb. 17,1972

[21] Appl.No.: 227,194

[52] U.S.Cl ..56/295,56/503 [51] Int.C|. ..A01d55/l8 [58] Field ofSearch56/295,255,503, l6.4,13.8

[56] 7 References Cited UNITED STATES PATENTS 2,547,540 4/1951 Roberts..56/255 2,697,322 12/1954 Watrous ..56/295 3,242,660 3/1966 Gary..56/13.8

1451 Nov. 21, 1972 3,482,380 12/1969 Stair ..56/295 3,538,692 11/1910Cope etal. ..56/295 Primary Examiner-Russell R. Kinsey Attorney-James A.Davis et al.

[57] ABSTRACT Rotary blade for a power-driven lawn mower comprising anelongate bodyterminating at each end in a plurality of integral cuttingfingers parallel to and displaced successively below and above the planeof the body with each finger defining a different plane and the uppersurfaces of the leading edges of the fingers and the lower surfaces oftheir trailing edges chamfered to form cutting edges, wherebytop-to-bottom reversal of the blade presents as leading cutting edgesthose that were trailing edges.

4 Claims, 4 Drawing Figures BACKGROUND OF THE INVENTION 1. Field of theInvention:

This invention relates in general to lawn mowers and more particularlyto a rotary blade for power-driven lawn mowers.

2. Description of the Prior Art:

The standard rotary blade for power-driven lawn mowers comprises anelongate body'having centrally disposed means attachable to thedepending end of a vertical drive shaft and a chamfered portion adjacentthe outer end of each leading edge for horizontal cutting. This effectsa single cutting of the grass substantially in the horizontal plane orrotation of the blade. It has been suggested to employ various otherblade configurations, but the simple single blade which has becomestandard seems to get the best results as compared to such other priorart blades, and sofar as is known, fine comminuting of the grass andsmall twigs and leaves to provide discharged material suitable forspreading on the cut lawn for mulching purposes has not been consideredto be attainable with only a single elongate blade in a power-drivenlawn mower. A plurality of blades have been suggested, but not for finecutting for mulching purposes. As an example, US. Letters Pat. No.3,162,990 employs an auxiliary guard attached to and disposed above theusual elongate blade that, although it includes an auxiliary horizontalcutting edge above and ahead of the regular blade, is provided solely asa safety precaution to prevent contact of the latter with solid largesize objects, which is accomplished by a plurality of radially spacedvertical guard fingers depending from' the auxiliary guard and extendingbelow the blade proper.

SUMMARY OF THE INVENTION A principal object of this invention is to aidin the ecology by means of a simple, inexpensive and longlived rotaryblade for power-driven lawn mowers which very finely comminutes thegrass and small twigs and leaves fallen on a lawn and spreads the finelycut material over the lawn for natural mulching purposes, therebyenhancing the growth and condition of the lawn and, at the same time,completely eliminating the usual raking, collection and disposal ofgrass cuttings and leaves, including the burning of leaves which now isor is being legislated against.

The blade of this invention comprises an elongate body having acentrally disposed socket for engagement with the lower end of thevertical drive shaft of any standard power-driven mower in substitutionfor its regular blade and adapted to be reversed top-to-bottom thereon,with a plurality of cutting fingers at each end parallel to anddisplaced successively below and above the plane of the body with eachfinger defining a different plane and the upper surface of the leadingedge and the lower surface of the trailing edge of each finger beingchamfered to form a cutting edge, and preferably with the total width ofthe fingers at each end being substantially equal to the width of thebody. In the drawings:

FIG. 1 is a perspective view of a lawn mower embodying the features ofthe invention;

FIG. 2 is a sectional view taken substantially on the line 2-2 of FIG.3;

FIG. 3 is an enlarged vertical sectional view through the axis of thedrive shaft; and

FIG. 4 is a detailed end elevation of the blade, as seen from the line4-4 of FIG; 3, and on an enlarged scale.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring particularly to FIG.1, reference numeral 11 indicates in general a lawn mower embodying thefeatures of this invention which includes the usual invertedwheel-mounted housing 12 open at the bottom and having a substantiallyvertical skirt or flange 13 with an opening or discharge aperture 14 atone side. This housing 12 supports the usual motor means 15 whichincludes a vertical drive shaft 16 depending through the housing 12 intothe inverted chamber defined thereby, as shown best in FIG. 3. Thisgeneral arrangement is that common to all currently commercial rotarypower-driven lawn mowers, and it is intended that the usual verticaladjusting means for varying the height of the housing be includedbetween the wheel means and the housing supported thereby.

This invention is directed to a rotary blade, indicated generally byreference numeral 17 (FIGS. 2 and 3), which is adapted to be mountedupon the depending end of the vertical drive shaft 16 in substitutionfor the standard cutting blade. This blade 17 comprises an elongate mainbody 18 having a centrally disposed socket drivingly engageable with theshaft 15 which, in the embodiment herein illustrated, is made up of apair of identical hub members 19 connected to each other and the mainbody 18 by nut and bolt means 21 and having a keyway for receiving theusual drive key 22 (FIG. 2) to insure positive driving connection withthe shaft 16 that has the usual complemental keyway. As shown in FIG. 3,a retaining bolt 23 is screwed into a suitable tapped receiving aperturein the drive shaft 16 and cooperates with a lock washer 24 for removablyretaining the rotary blade 17 on the drive shaft 16. Thus, merely byremoving the retaining bolt 23, the rotary blade 17 may be slid off ofthe drive shaft 16, reversed top-to bottom, and replaced on the driveshaft in inverted position where it will be positively retained merelyby reinserting the retaining bolt 23 with its lock washer 24.

At each of its ends, the main body 18 of the blade 17 terminates in aplurality of cutting fingers 25, 26, 27 and 28 which are parallel toeach other and the main body 18 and displaced successively below andabove the plane of that main body, with each finger defining a differentplane. More specifically, with the direction of rotation of the blade 17being clockwise as indicated by the arrow shown in FIG. 2, the finger 25is the leading finger and as shown in FIGS. 3 and 4, is displaced belowthe main body 18. As best seen in FIG. 3, the center line distancebetween this leading finger 25 and the plane of the main body 18 isdesignated by the dimension x, it being observed that the major portionof the finger is substantially horizontally disposed and is joined tothe main body 18 by an inner curved portion.

The next finger 26 adjacent the leading finger 25 is displaced above theplane of the main body 18 a distance designated in FIG. 3 by thedimension y. As will be observed from that Figure, such distance ybetween the center lines of the main body portion 18 and the secondcutting finger 26 is twice the distance x. The third cutting finger 27next adjacent and trailing the second finger 26 is displaced below theplane of the main body 18 the same distance y as is the second finger 26disposed above the main body. The fourth or last trailing finger 28 isdisplaced above the main body 18 the same distance x as is the firstfinger 25 below the main body. It will be appreciated, of course, thatwhile these several cutting fingers 25-28 are disclosed herein as beingintegral extensions of the main body 18, it is contemplated that thesame may be formed separately and attached to the main body in anysuitable manner. As best seen in FIG. 2, the total of the widths ofthese fingers 25-28 at each end of the main body 18 substantially equalsthe width of the main body.

The upper surface of the leading edge of each of these fingers 25-28 ischamfered at 29 to form a cutting edge, and the lower surface of thetrailing edge of each of these fingers similarly is chamfered at 31.Thus, when the blade is mounted as illustrated herein, rotation thereofin the usual manner results in the chamfered upper portions 29functioning as leading cutting edges, and when the blade is reversedtop-to-bottom on the drive shaft 16, the chamfered portions 31 will thenbe disposed as leading cutting edges. And, with the vertical offsettingof the cutting fingers 25-28 as hereinbefore described, the leadingfinger, whether 25 with the blade mounted as herein illustrated or 28following a top-to-bottom reversal, will have its cutting edge 29 or 31disposed the smaller distance x from the main body 18, and the thirdcutting finger 27, or the second cutting finger 26 if the blade has beenreversed top-tobottom, will have their cutting edges 29 or 31,respectively, disposed below the main body 18 the greater distance y.Thus, the two lower cutting fingers at each end of the main body 18 willsuccessively sever upstanding blades of grass incrementally, with theleading such blade first chopping off the upper ends of the grass bladesfollowed by a cutting therefrom by the-trailing lower finger of grassblade sections having lengths x. The cut end portions of the grassblades so severed will be deflected by these lower cutting fingersupwardly into the paths of the upper cutting fingers 26,28 or 27,25, asthe case may be, for further comminuting action. The same style ofcomminuting of leaves and small twigs that have fallen onto the surfacesof the lawn will similarly be effected, and the cutting fingers 25-28 ateach end of the main body 18 will function in the same manner. With thisarrangement, communinuting of the grass and small twigs and leaves issufficiently fine before being discharged by virtue of the rotary actionof the blade 17 through the aperture 14 that the discharged material issuitable and extremely advantageous for mulching purposes. Therefore, itis unnecessary to collect the material discharged from themower, and theusual raking, collection and disposal of grass cuttings and leaves fromthe lawn, including the in top-to-bottom reversed position which thenwill present the previous trailing chamfered surfaces 31 as th 1 adincuttin ed es on e fin er 25-28 it is lhflfight tha t thi s inversion aiid fnany of its attendant advantages will be understood from theforegoing description, and it will be apparent that various changes maybe made in the form, construction and arrangement of the parts withoutdeparting from the spirit and scope of the invention or sacrificing allof its material advantages, the form hereinbefore described being merelya preferred embodiment thereof.

I claim:

1. A rotary blade for a power-driven lawn mower having a verticallydepending drive shaft, comprising an elongate main body having acentrally disposed socket drivingly engaging said shaft, said bodyterminating at each end in a plurality of cutting fingers parallel toand displaced successively below and above the plane of said body witheach finger defining a different plane, the upper surface of the leadingedge and the lower surface of the trailing edge of each of said fingersbeing chamfered to form a cutting edge, whereby top-to-bottom reversalof said blade presents as leading cutting edges those that were trailingedges.

2. A rotary blade according to claim 1, wherein the total of the widthsof said fingers at each end of said body substantially equals the widthof said body.

3. A rotary blade according to claim 1, wherein said fingers areintegral extensions of said body.

4. In a mulching lawn mower, comprising an inverted housing open at thebottom and having a substantially vertical skirt supported by wheelmeans a predetermined distance from the ground to define a chamber withan opening at one side defining a mulch discharge aperture, motor meansmounted on said housing, and a vertical drive shaft rotated by saidmotor means and depending through said housing into said chamber; andelongate blade having a centrally disposed socket drivingly engaging thelower end of said shaft to position said blade in approximatelyhorizontal alignment with the vertical center of said dischargeaperture, said blade terminating at each end in a plurality ofhorizontal fingers each defining a different plane disposed successivelybelow and above said vertical center of said discharge aperture, and theupper surface of the leading edge and the lower surface of the trailingedge of each of said fingers being chamfered to form a cutting edge,whereby top-to-bottom reversal of said blade presents as leading cuttingedges those that were trailing edges and rotation of said blade as themower is moved on said wheel means results in mulching within saidchamber of grass, leaves and small twigs encountered by said blade anddischarging thereof through said aperture to spread the same overadjacent ground areas.

1. A rotary blade for a power-driven lawn mower having a verticallydepending drive shaft, comprising an elongate main body having acentrally disposed socket drivingly engaging said shaft, said bodyterminating at each end in a plurality of cutting fingers parallel toand displaced successively below and above the plane of said body witheach finger defining a different plane, the upper surface of the leadingedge and the lower surface of the trailing edge of each of said fingersbeing chamfered to form a cutting edge, whereby top-to-bottom reversalof said blade presents as leadiNg cutting edges those that were trailingedges.
 1. A rotary blade for a power-driven lawn mower having avertically depending drive shaft, comprising an elongate main bodyhaving a centrally disposed socket drivingly engaging said shaft, saidbody terminating at each end in a plurality of cutting fingers parallelto and displaced successively below and above the plane of said bodywith each finger defining a different plane, the upper surface of theleading edge and the lower surface of the trailing edge of each of saidfingers being chamfered to form a cutting edge, whereby top-to-bottomreversal of said blade presents as leadiNg cutting edges those that weretrailing edges.
 2. A rotary blade according to claim 1, wherein thetotal of the widths of said fingers at each end of said bodysubstantially equals the width of said body.
 3. A rotary blade accordingto claim 1, wherein said fingers are integral extensions of said body.